Stable lubricating composition and inhibitor mixture therefor



United States Patent Ofifice Patented Nov. 1, 1968 This application is related to and a continuation-in-part of US. patent application, Serial No. 241,049, filed November 29, 1962, now abandoned, for Stable Lubricating Composition and Inhibitor Mixture Therefor.

This invention relates to lubricants. More particularly, it relates to the problem of inhibiting oxidative degradation of lubricants, particularly synthetic, ester base, lubricants at temperatures up to about 500 F.

This invention comprises a mixture consisting essentially of (1) phenyl-a-naphthylamine and (2) a diphenylamine selected from the group consisting of diphenylamine, N"(C1C8 a1kyl)-diphenylamines and para substituted monoand di(C C alkyl)-diphenylamines and para substituted monoand di[(C -C alkyl) phenyl]- diphenylamines, the weight ratio of the phenyl-a-naphthylamine to the diphenylamine being in a range from about 4:1 to about 1:4. This mixture is a highly effective antioxidant and corrosion inhibitor composition for lubricants of both the petroleum base type and the synthetic ester base type.

Hence, this invention comprises a lubricating composition consisting essentially of (A) a lubricant and (B) said mixture at a protective concentration relative to oxidation and corrosion. In the case of most lubricants, satisfactory results are obtained when the concentration of the mixture is in a range from about 0.005 to about 2% by weight of the lubricant. However, higher and lower concentrations can be employed.

This invention is further illustrated by the following examples of various aspects thereof, including specific embodiments of the invention. This invention is not limited to these specific embodiments unless otherwise indicated.

EXAMPLES 1-4 These examples illustrate specific embodiments of the inhibitor composition of this invention.

The formulations of these specific embodiments are:

Example 1.Formulatin Phenyl-u-naphthylamine Alkylated styrenated diphenylamine product 80 The alkylated styrenated diphenylamine product is a mixture marketed as Goodrite Staylite. The mixture is made according to the US. patent, No. 2,530,769, to Hol lis. In brief, it is a normally liquid, oily product consisting essentially of (l) p,p-di-t-octyldiphenylamine, (2) p,p-di-a-phenethyldiphenylamine, (3) p t octyl-p-aphenethyldiphenylamine, (4) p mono-t-octyl-diphenylamine and (5) p-mono-a-phenethyldipheny1amine in the ratio of 50-70% by weight of (1), (2) and (3) to 30- 50% by weight of (4) and (5), said product resulting from the reaction of 1.3 to 2.0 chemical equivalents of a hydrocarbon mixture containing diisobutylene and styrene in the ratio of 2-5 parts by weight of diisobutylene to 1 part by weight of styrene, with 1 chemical equivalent of diphenylamine with the aid of a Friedel-Craft condensation catalyst such as aluminum chloride, at a temperature of ISO-200 C.

The specific compositions of these formulations are prepared by admixing the components thereof at 20 25 C.

EXAMPLES 5-10 These examples illustrate specific embodiments of a synthetic ester type lubricant composition of this invention.

The formulations of these embodiments are:

Example 5.-Formulati0n Components: Parts by weight Bis(2,2,4-trimethylpentyl)azelate Inhibitor composition of Example 1 1 Example 6.F0rmulatian Components: Parts by weight Bis(2,2,4-trimethylpentyl)azelate 100 Inhibitor composition of Example 2 1 Example 7 .F ormulation Components: Parts by weight 2,2,4-trimethylpentanediol-1,3-dipelargonate 100 Inhibitor composition of Example 1 1 Example 8.F0rmulation Components: Parts by weight 2,2,4-trimethylpentanedio1-1,3-dipelargonate 100 Inhibitor composition of Example 2 1 Example 9.-F0rmulati0n Components: Parts by weight 2,2,4-trimethylpentanediol 1,3 dipelargonate 99.375

Inhibitor composition of Example 3 0.625

Example 10.F0rmulati0n Components: Parts by weight 2,2,4-trimethylpentanediol 1,3 dipelargonate 99.375

Inhibitor composition of Example 4 0.625

The specific lubricant compositions of the foregoing examples are prepared by admixing the components thereof at 20 C. In this connection, in each case the lubricant composition can be prepared by adding the inhibitor composition to the ester base stock or the individual components of the inhibitor composition can be admixed simultaneously or sequentially with the ester base stock.

Test samples of the foregoing specific, synthetic lubricant compositions and other specific, synthetic lubricant compositions have actually been tested for resistance to oxidative degradation and for inhibition of corrosion.

One test employed was a 347 F. corrosion and oxidation induction test. In the procedure of this test a 125 milliliter test sample of the lubricant composition to be at which the acid number of the lubricant begins to rise rapidly in comparison to time.

In the first set of test samples, bis(2,2,4-trirnethylpentyl) azelate, a dibasic acid ester, was the lubricant. The test samples were prepared by admixing with this synthetic ester base stock the additives at the concentrations indicated in the following Table I. The test results and tested s introduced into a large test tube. Five metal observations are summarized in Table I.

TABLE I Concentra- Concentra- Concentration of tion of tion of Dirtiness Rating Metals Weight Loss in rng./cm. and Corrosion at 72 Hours Sampl Phenyl-a- Diplienyl- N-methyl Useful at 72 Hours No. naphthylamine in diphenyl- Life in amine percent by amine in Hours in percent weight of percent by by wt. of lubricant wt. of Test Sam- Metal Magnesium Aluminum Copper Steel Silver lubricant lubricant Tube ple Blanks 0 0 72 Light Slight; Olean 36-SC 0 00-N 1. 3-80 0. 03-N 0. 00-N 0. 50 0 0 90 Clean Clear N one 0. 00-N 0 00-N 0. 07-N 0. Ol-N 0. 01-N 1.00 0 0 400 -do do do- 0.00-N 0 Ol-N 0.03-N 0.02N 0.02N 0 0.50 0 90 d0 do do 0.00N 0 01-N 0.14-N 0.0lN 0.03-N 0 1. 00 0 260 do do do 0.00-N 0 00N 0.1l-N 0 00-N 0.00-N 0.25 0. 0 165 0 do do 0.00-N 0 Ol-N 0. Ol-N 0.01-N 0.01-N 0. 0. 50 0 740 do do d0. +0.02-N 0 01-N 0. 07-N 0 02N 0. 02N 1. 00 1.00 0 740 dodo do 0. 00- 0 Ol-N 0.02-N 0 02N 0. 02N 0 0 1 00 do do d0 +0 (ll-N 0 00-N 0. l3-N 0. 00-N 0.0 N 0. 50 0 0 50 180 0 do 0 0 0 0 N 0.07-N 0.01-N 0.0l-N

blanks of magnesium alloy, aluminum alloy, copper, steel and electrolytic silver are tied together into a bisected parallelogram structure. The structure is then introduced into the lubricant composition in the test tube. An air tube is inserted into the test tube and air is passed through the sample of lubricant composition at a rate of five liters per hour while the temperature of the sample is established and maintained at 347 F. After the test sample has been aerated at this temperature for 72 hours, a specimen is removed and e acid number of the specimen is determined. The test tube, lubricant and metal blanks are inspected for dirtiness. In addition, the metal blanks are checked for corrosion and weight loss. The metal blanks are then reinserted into the lubricant sample in the test tube and aeration is continued. Periodically, specimens of the lubricant are withdrawn from the test tube and their acid numbers determined. A plot is made from the acid number data in order to determine the stable life or useful life of the lubricant composition.

The stable life or useful life end point of the lubricant 45 composition under the conditions of this test is the time In the foregoing Table I the symbol SC indicates severe corrosion While N indicates no corrosion.

Sample 7, it will be observed, corresponds to the specific composition of Example 3 while Sample 10 corresponds to the specific composition of Example 4.

The data of Table I shows that the specific inhibitor compositions of this invention are highly effective in protecting a synthetic ester base lubricant against oxidative degradation and in minimizing corrosion. Moreover, comparison of the useful life of Sample 7 with the useful lives of Samples 2 and 4, and the useful life of Sample 8 with Samples 3 and 5 reveals synergism on the part of the inhibitor composition or mixture of this invention.

In the second set of test samples, 2,2,4-trimethylpentanediol-1,3-dipelargonate, and ester of a glycol and a m-onobasic or monocarboxylic acid, was the lubricant. The test samples were prepared by admixing with this synthetic ester base stock the additives at the concentrations indicated in the following Tables II and III. The test results and observations are summarized in Tables II and III.

TAB LE II Concentra- Concentra- Concentra- 4 tion of tion of tion of Dirtiness Rating Metals Weight Loss in mg./crn. and Corrosion at 72 Hours Sample Pheuyl-a- Diphenyl- N -methyl Useful at 72 Hours No. naphthylairline in diphenyl- Life in amine percent by amine in Hours in percent weight of percent by by wt. of lubricant Wt. of Test Sarn- Metal Magnesium Aluminum Copper Steel Silver lubricant lubricant Tube ple Blanks 0 0 0 0. 0025 0 0 0. 050 0 0 0. 0 0 0. 50 O 0 1. 000 0 0 O 0. 050 0 O O. 125 0 0 O. 250 0 0 O. 50 0 0 1. 00 O 0. 0025 0.0025 0 0. 050 0.050 0 0. 125 0. 125 0 O. 125 0. 250 0 0. 125 0. 50 0 0. 250 0. 250 0 0. 50 0. 125 0 0. 5O 0. 50 O 0. 50 1. 00 0 1. 00 0. 50 0 1. 00 1. 00 0 0. 0 0 1. 00 +0. 05-N 0. 02N 0. 5O 0 0. 50 166 do do do. +0. 02N +0. 03-N +0. 03N +0. 02N +0. 02N

In the foregoing Table II, H.C. means heavy corrosion, N" means no corrosion, S slight corrosion (in the one case there was one pit), C .rneans corrosion and HE. signified heavy electrolytic effect.

6 Another test employed is the 325 F. lead corrosion test described in Federal Test Method Standard No. 791. This test is an indication of the corrosiveness of the lubricant composition to lead-indium bearings both before and p it Will be obsrved, wrfespon'ds to 5 after storage under accelerated conditions. Two weeks fi il f Example 5 -1 6 Sample 24 corresponds storage at 185 F. has been roughly equated to a storage to Th gi tg o f ib ii ifgg gns'trat s t the inhibitor of one year under tropical conditions, while 45 days of m.xture of invention t oncennrations in a ran 6 storage at 185 F. has been equated to an actual storage 1 S is a c g of three years under tropical conditions. from about 0.005 to about 2% by weight of the lubricant In the first set of Sam 16s sub.ected to the F 16 d are highly eifective in protecting ynthetic ester base type t t th 1 b p t 2 2 4 t th 1 i lubricants against oxidative degradation and in minimizf f e ulncan was time P'P ing corrosion. Moreover, comparison of the useful lives f samp w Prepaled by z t thls of Samples 1342 with the useful lives of Samples lubricant with the additives at the concentrations indicated reveals that the inhibitor mixtures of this invention are 15 the followlng Table The test results are set forth synergistic in effect. In Table 7 7 TABLE IV 7 Concentration Concentration Concentration Weight Loss of Lead in mgJin.

of Phenyl-aof Diphenylof N-methyl Naphthyp amine in Diphenyl- Sample No amine m percent by amine 1n Stored 14 Stored 45 percent, by weight of percent by Initial Days at Days at weight of lubricant weight of 185 F. 185 F. lubricant lubricant TABLE III I I Concentration Sample in Table IV, it will be noted, is identical to the g ,i 5 2332? Useful 35 formulation of Example 3 while sample 10 is identical Sample Naphthylamino diplienylamine Diphenylamine Life in to the formulation of Example 4,

N 0. in percent by in percent by Product in Hours Iveight of {vegght of percegt biv The data of Table IV show the excellent corrosion in- 'cnt Wei 0 ubrmnt u n a lubigicant hibition properties of the specific, inhibitor compositions 40 or mixtures of this invention. 8 8 8 2 In the second set of samples subject to the 325 P. 8.500 8 195 8 22 lead corrosion test the lubricant was 2,2,4-trimethyl peng 8.23 8 33 tanediol-l,3-dipelargonate. The samples were prepared 0: 50 01125 8 195 130 by admixing this lubricant with the additives at the con- 0 5 8 0 0.50 30 centrations indicated in the following Table V. The test 1' 2 81% 8 3; i3, $8 results are set forth in Table V.

TABLE V Concentration of Concentration of Concentration of Weight Loss of Leadinmg/in. Plignlyl-q-Naph- Diplienylagrlnne lgI-melthyl Di- Y 9.1111116 111 111 DGTCBH y p eny amine 1D Sample percent by weight of percent by Stored 14 Stored 45 0. Weight; of lubricant weight of Initial Days at Days at lubricant lubricant 185 F. 185' 0. 00 0. 00 0. 00 40 40 42 2.-- 0. 0. 00 0. 00 +0. 4 +0.2 +0. 4 3 1. 00 0. 00 0. 00 +0. 9 +1. 5 +0.7 4-.- 0. 00 0. 05 0. 00 +0.3 2. 4 1. s 5 0. 00 1. 00 0. 00 +0. 5 0. 3 1. 7 i 0. 25 0. 25 0. 00 1. 3 .+1. 0 +0.8 7 0. 50 0.50 0. 00 +1.1 +1. 7 +0. 8 1. 00 i. 00 0. 00 +2. 0 0.1 +0. 1 9 0. 00 0. 00 1. 00 0. 1 6. 9 7. 3 10 0. 50 0. 00 0. 50 +0.1 0. 2 +0. 2

Sample 7, it will be observed, corresponds to the formulation of Example 9 while sample 10 corresponds to the formulation of Example 10.

The data of Table III likewise demonstrate that the inhibitor mixtures of this invention at concentrations in a range from about 0.005 to about 2% by weight of the lubricant are highly efiective in protecting synthetic ester base type lubricants against oxidative degradation.

Moreover, comparison of the useful lives of samples 6 and 7 with the useful lives of samples 2-5 and the useful lives of samples l01l with the useful lives of samples 23 and 89 reveals that the inhibitor mixtures of this invention are synergistic in eflect.

Other features, advantages and specific embodiments of this invention will be readily apparent to those in the exercise of ordinary skill in the art after reading the foregoing disclosures. In this connection, while this invention has been described in considerable detail relative to specific embodiments thereof, variations and modifications of these embodiments can be efiected within the spirit and scope of the invention as disclosed and claimed.

The embodiments of the invention in which-an exclusive property or privilege is claimed are defined as follows:

1. An inhibitor composition consisting essentially of phenyl-a-naphthylamine and a diphenylamine selected from the group consisting of diphenylamine and a alkylated styrenated diphenylaminqthe weight ratio of one to the other being in a range from about 4:1 to about 1:4; said alkylated styrenated diphenylamine consisting essentially of 1) p,p-di-t-octyldiphenylamine, (2) p,p'-di-aphenethyldiphenylamine, (3) p-t-octyl-p-a-phenethyldiphenylamine, (4) p-mono-t-octyl-diphenylamine and (5) p-mono-a-phenethyldiphenylamine in the ratio of 5070% by weight of (l), (2) and (3) and 3050% by weight of (4) and (5).

2. An inhibitor composition consisting essentially of phenyl-wnaphthylamine and diphenylamine at a weight ratio in a range from about 4:1 to about 1:4.

3. An inhibitor composition consisting essentially of phenyl-ot-naphthylamine and an alkylatcd styrenated diphenylamine product at a Weight ratio in a range from about 4:1 to about 1:4; said alkylated styrenated diphenylamine consisting essentially of 1) p,p'-di-t-octyldiphenylamine, (2) p,p'-di-ot-phenethyldiphenylamine, (3) p-toctyl-p'-zx-phenethyldiphenylamine, (4) p-mono-toctyldiphenylamine and (5) p-mono-ix-phenethyldiphenylamine in the ratio of 50-70% by weight of (1), (2) and (3) and 3050% by weight of (4) and (5).

4. A lubricant composition consisting essentially of a lubricant and, at an oxidation and corrosion inhibiting concentration, a mixture consisting essentially of phenyla-naphthylamine and a diphenylamine selected from the group consisting of diphenylamine and alkylated styrenated diphenylamine, the weight ratio of one to the other being in a range from about 4:1 to about 1:4;

said alkylated styrenated diphenylamine consisting essentially of (,1) p,p-di-t-octyldiphenylamine, (2) p,p'-di-aphenethyldiphenylamine, (3) p-t-octyl-p'-u-phenethyldiphenylamine, (4) p-mono-t-octyl-diphenylamine and (5) p-mono-x-phenethyldiphenylamine in the ratio of 50-70% by weight of (1), (2) and (3) and 3050% by weight of (4) and (5).

5. A lubricant composition consisting essentially of a synthetic ester lubricant and, at a concentration in a range from about 0.005 to about 2% by weight of said lubricant, a mixture consisting essentially of phenyl-ot-naphthylamine and a diphenylamine selected from the group consisting of diphenylamine, and alkylated styrenated diphenylamine, the weight ratio of one to the other being in a range from about 4:1 to about 1:4; said alkylated styrenated diphenylamine consisting essentially of (1) p,p'-di-t-octylcliphenylamine, (2) p,p'-di-a-phenethyldi'- phenylamine, (3) p-t-octyl-p'-a-phenethyldiphenylainine, (4) p-mono-t-octyl-diphenylamine and (5) p-mono-aphenethyldiphenylamine in the ratio of 50-70% by weight of (l), (2) and (3) and 3050% by weight of (4) and (5).

6. A lubricant composition consisting essentially of an ester base stock consisting essentially of 2,2,4-trimethyl pentanediol-l,3-dipelargonate and, at a concentration in a range from about 0.005 to about 2% by weight of said stock, a mixture consisting essentially of phenyl-a-naphthylamine and diphenylamine at a weight ratio in a range from about 4: l to about 1:4.

7. A lubricant composition consisting essentially of an ester base stock consisting essentially of bis(2,2,4-trimethylpentyl)azelate and, at a concentration in a range from about 0.005 to about 2% by weight of said stock, a mixture consisting essentially of phenyl-a-naphthylamine and diphenylamine at a Weight ratio in a range from about 4:1 to about 1:4.

8. A lubricant composition consisting essentially of an ester base stock consisting essentially of 2,2,4-trimethylpentanediol-l,3-dipelargonate and, at a concentration in a range from about 0.005 to about 2% by weight of said stock, a mixture consistingessentially of phenyl-ot-naphthylamine and an alkylated styrenated diphenylamine product at a weight ratio in a range from about 4:1 to about 1:4; said alkylated styrenated diphenylamine consisting essentially of (1) p,p'-di-t-octyldiphenylamine, (2) p,pdi-a-phenethyldiphenylamine, (3) p-t-octyl-p'-aphen'ethyldiphenylamine, (4) p-mono-t-octyl-diphenylamine and (5 p-mono-a-phenethyldiphenylamine in the ratio of 50-70% by weight of (1), (2) and (3) and 3050% by weight of (4) and (5).,

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 750,560 6/1956 I Great Britain.

OTHER REFERENCES Cohen, George: Aliphatic Esters; Industrial and Engineering, volume 45', August 1953, pp. 1766-1774.

DANXEL E. WYMAN, Primary Examiner.

C. O. THOMAS, P. E. KONOPKA, Assistant Examiners. 

4. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF A LUBRICANT AND, AT AN OXIDATION AND CORROSION INHIBITING CONCENTRATION, A MIXTURE CONSISTING ESSENTIALLY OF PHENYLA-NAPHTHYLAMINE AND A DIPHENYLAMINE SELECTED FROM THE GROUP CONSISTING OF DIPHENYLAMINE AND ALKYLATED STYRENATED DIPHENYLAMINE, THE WEIGHT RATIO OF ONE TO THE OTHER BEING IN A RANGE FROM ABOUT 4:1 TO ABOUT 1:4; SAID ALKYLATED STYRENATED DIPHENYLAMINE CONSISTING ESSENTIALLY OF (1) P,P''-DI-T-OCTYLDIPHENYLAMINE, (2) P,P''-DI-APHENETHYLDIPHENYLAMINE, (3) P-T-OCTYL-P7-A-PHENETHYLDIPHENYLAMINE, (4) P-MONO-T-OCTYL-P-A-PHENETHYLDIP-MONO-A-PHENETHYLDIPHENYLAMINE IN THE RATIO OF 50-70% BY WEIGHT OF (1), (2) AND (3) AND 30-50% BY WEIGHT OF (4) AND (5). 